I used to scream and throw expensive clothing at salesladies who dared to "peek" through the slats of a dressing room door to ask if I needed anything. I have never imagined that the majority of men were actually any happier about a lack of privacy, but as you pointed out, maybe the naked swimming thing was helpful - really, we all have similar parts, except for reproductive organs, and eventually, sooner or later, we learn about those, too. I'm not sure what the answer is - be less hung up about nudity or more protective of EVERYONE's privacy/modesty.
And I totally agree with you that no one, male or female, should be shamed or dominated through their body image or involuntary exposure of their body parts. It is a form of sexual violence, and it's not right or better when the victim is a boy or a man.